In the oil and gas exploration and production industry, there are many occasions where downhole well bore operations require a tool or the like to be temporarily secured at a predetermined depth. For example, a logging or intervention tool string or the like may be required to be run into a well bore to the required depth and subsequently secured in place to perform a well bore procedure, operation, test or the like. In such cases it is important to ensure that sufficient support to the tool string is established when located at the required bore depth, and also that the tool string can be readily retrieved to surface level. Various tool forms have been proposed for use in creating a well bore support, such as that described in the applicant's international patent application, publication number WO 02/04783, which relies on a number of slips which are caused to extend radially outwardly by a cam and ramp arrangement into engagement with a bore wall.
Additionally, many downhole operations may require a section of the well bore to be isolated from well bore and other fluids, such as drilling fluids and the like. Such well bore isolation may be required where bore wall testing or repair must be carried out, for example, repairing or re-establishing a suitable liner hanger or the like or, for example, perforating a section of liner to improve or increase production flow rates. In such occasions, it may be necessary not only to provide a sufficient level of sealing, but also to provide adequate support while the seal is being set and optionally while the seal is established, until no longer required. Applicant's above noted international patent application further discloses such a seal arrangement, which may be deformed so as to extend outwardly of the tool and into sealing engagement with the bore wall.
However, it is sometimes the case with existing downhole tools proposed for being secured in a well bore, and optionally providing a form of bore sealing, that ineffective or insufficient support or sealing is established. This inefficiency may be caused by failure to provide adequate radial expansion of the tool, or portion of the tool, to establish a significant level of interference with the bore wall which is sufficient to provide support and/or the necessary bore sealing.
Accordingly there is need in the art for improved retention of downhole tools in well bores.